1 #include <stdio.h>
2 #include <iostream>
3 #include <math.h>
4 #include <algorithm>
5 using namespace std;
6
7 struct point
8 {
9 double x,y;
10 };
11 point a[105][2];//a[i][0]代表第i条线段的头，a[i][1]代表尾
12
13 double fan(double x,double y)
14 {
15 return x>y?x:y;
16 }
17
18 double fin(double c,double d)
19 {
20 return c<d?c:d;
21 }
22
23 double cnt(point a,point b)
24 {
25 return sqrt((a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y));
26 }
27
28 int is(point a,point b,point c,point d)
29 {
30 if(a.x==b.x&&c.x==d.x)
31 {
32 return 0;
33 }
34 if(a.x==b.x&&c.x!=d.x)
35 {
36 double m1=a.x;
37 double m2=(a.x-c.x)*(d.y-c.y)/(d.x-c.x)+c.y;
38 if(m1<=fan(a.x,b.x)&&m1>=fin(a.x,b.x)&&m2>=fin(a.y,b.y)&&m2<=fan(a.y,b.y)&&m1<=fan(c.x,d.x)&&m1>=fin(c.x,d.x)&&m2>=fin(c.y,d.y)&&m2<=fan(c.y,d.y))
39 return 1;
40 }
41 if(c.x==d.x&&a.x!=b.x)
42 {
43 double m1=c.x;
44 double m2=a.y+(b.y-a.y)*(c.x-a.x)/(b.x-a.x);
45 if(m1<=fan(a.x,b.x)&&m1>=fin(a.x,b.x)&&m2>=fin(a.y,b.y)&&m2<=fan(a.y,b.y)&&m1<=fan(c.x,d.x)&&m1>=fin(c.x,d.x)&&m2>=fin(c.y,d.y)&&m2<=fan(c.y,d.y))
46 return 1;
47 }
48 double k1=(b.y-a.y)/(b.x-a.x);
49 double k2=(d.y-c.y)/(d.x-c.x);
50 double m1,m2,x,y;
51 if(k1==k2) return 0;
52 else
53 {
54 m1=a.y-k1*a.x;
55 m2=c.y-k2*c.x;
56 x=(m1-m2)/(k2-k1);
57 y=k1*x+m1;
58 if(x<=fan(a.x,b.x)&&x>=fin(a.x,b.x)&&y>=fin(a.y,b.y)&&y<=fan(a.y,b.y)&&x<=fan(c.x,d.x)&&x>=fin(c.x,d.x)&&y>=fin(c.y,d.y)&&y<=fan(c.y,d.y))
59 return 1;
60 }
61 return 0;
62 }
63
64 int main()
65 {
66 int cas = 1;
67 int n,i,j;
68 while(~scanf("%d",&n),n)
69 {
70 int cnt = 0;
71 for(i = 0;i<n;i++)
72 scanf("%lf%lf%lf%lf",&a[i][0].x,&a[i][0].y,&a[i][1].x,&a[i][1].y);//线段的首尾坐标
73 for(i = 0;i<n;i++)
74 {
75 for(j = i+1;j<n;j++)
76 {
77 if(is(a[i][0],a[i][1],a[j][0],a[j][1]))
78 cnt++;
79 }
80 }
81 printf("%d\n",cnt);
82 }
83
84 return 0;
85 }
